Friday, October 13, 2006

Biofuels Revisited

“Fletcher continues leadership on energy independence”“USDA and DOE Fund Biomass Research Projects”“$17.5 million for biofuels”“Harvesting Sunshine for Biofuels”“Biodiesel proves its worth with bus fleet (KRTB)”

Some articles from around the internet. Bio-diesel is supposed to save us from fossil fuels. Bio-diesel will grow our way to sustainable energy. It’s the new clean green “way-of-the-future”. The people who aren’t onboard are “oil-lackeys” or “not aware” of fossil fuel’s limitations. They are standing in the way of our bright future. They are the reasons why we’re still dependent on foreign oil. They’re the reason why investors haven’t flocked to the farms. Yeah. Them. Oil lackeys. Bio-diesel is supposed to power our civilization in an eco-friendly way. Will it?

I’ve always been skeptical. Actually, I’ve been derisive. The world burns 50 million barrels of oil per day. The US burns 20 million of those barrels. A barrel of crude oil weighs136kg, so annually we (US) go through about 1 Gtonne of oil per year. 1E12 kg/year. That’s the finish line. If you want to replace the energy we get from fossil fuels, you have to play on that degree of scale. As I’ve pointed out in previous posts that’s a no if’s ands or buts condition. We either generate that level of energy, or we all get a lot poorer and possibly subservient to those nations that manage to hold onto the oil. Civilization is not magically going to morph into some radically “efficient” form where people don’t need to eat, drink clean water, run factories, or ship goods. Can we get here from there growing corn?

Subjectively, when I think of the fields behind my house, the breadbasket of the world, I can’t imagine that something harvested only once a year could possibly add up to that kind of mass. Could a field even fuel the tractor that harvests it? It doesn’t look like it to me.

But let’s run the numbers. According to http://www.ag.ndsu.edu/pubs/plantsci/rowcrops/a834w.htm, North Dakota gets about 121 bushels of corn per acre.

For soybeans, it’s around 40 bushels/acre. That’s industrialized, fertilized, mechanically planted and harvested soybeans. The “organic” (as if industrial agriculture is inorganic!) counterparts to soybeans rate around 16 bushels/acre. http://www.energybulletin.net/1469.html. And that’s from an approving site!

Now, a bushel is an amount by volume measurement. A bushel of soybeans is around 60 lbs. That translates into 1.1 tonnes soybeans/acre. http://www.smallgrains.org/springwh/June03/weights/weights.htm Corn is about 56 lbs/bushel, or 3.04 tonnes/acre. Of course, that’s tonnes of actual corn. The North Dakota site gives around 16 tonnes of silage, and I assume that a fermenting reactor is not particular about which bit it eats.

But you have to alternate corn and soybeans each year, otherwise you wear out your soil. You can’t go overfarming your land without crop rotation, unless you want to set off another dust bowl and ruin our ability to feed the world. So, assuming that you can just go corn/soybean/corn/soybean ad infinitum without consequence, you’d have an average of 8.5 tonnes/acre.

If a tonne of produce could magically be transformed into a tonne of crude oil, then we’d need to farm 117 million acres constantly.

http://www.nationmaster.com says the following about our agricultural statistics:We have 179,000,000 hectares of permanent arable cropland. We currently grow corn on 28,710,000 of these hectares. Soybeans on a similar area (expectedly). And of course, we’re well to the top of both of these charts, worldwide.

So basically, we would need to devote land on the order of 27% of our arable land to bio-diesel production to make this work, assuming 100% efficiency in food to fuel conversion!!! We’d need to double the portion of our country devoted to corn and soybean production! And, as you all know, assuming 100% efficiency is a good way to be completely divorced from reality.

(Side note – America’s farmland is actually doing far better in the analysis at this point than I initially expected. It just goes to show that you always have to run the numbers when talking about this degree of scale. Humans do not instinctively think in terms of quantities on this degree of scale. We can’t extrapolate from things that we’re familiar with, on our personal visual scale, onto levels of national production, without resorting to a lot of math.)

Next to get an idea of the efficiencies involved, I’ll reference this article that caught my eye – “The Path Forward for Biofuels and Biomaterials”, Science Magazine, 27 Jan 2006. This article talks about harvesting wood for bio-materials. They are looking at something like 10-20 tonnes/hectare for woody crops, about on par with corn. (Though I imagine, far more involved and energy intensive to harvest). I hope they are including a suitable crop-rotation time for the forests to grow back, or we’ll denude our continent for a decade or so of fuel.

They claim that a process involving super-critical steam can break up 57-77% of their bio-mass in their hypothetical bio-refinery into condensable gasses, which can further be processed into syngas (% not given), which can finally be processed into Biofuels.

I think the Fischer-Tropsch process is commonly mentioned as a last-step in the creation of biofuels. Fischer-Tropsch can also process coal and other materials into fuel. For this DOE paper (http://www.fischer-tropsch.org/DOE/DOE_reports/NREL/TP-431-8143/TP-431-8143-1_sec1.pdf) it seems as if the maximum theoretical stochiometric efficiency of coversion is around 39.3%.

Stochiometric efficiency isn’t by mass efficiency. It looks like they’re measuring mols hydrogen per mol biomass. CH1.47O0.67. Looks like it would relate to a hydrocarbon CnH2n with something like a 40% or 30% by mass ratio.

So the overall process is looking like it’s around 25 – 30% efficient by mass. For brevity (and due to time constraints), I won’t consider harvesting, transporting, or the energy costs of refinement. We will need around 400 million acres of farmland to replace our gasoline consumption. We would need to be using something like 90% of those 179 million arable hectares for biodiesel production.

I don’t think we’ll be able to replace gasoline with bio-diesel. I’ll admit that I didn’t imagine it would even end up in the neighborhood, but it seems our nations maximum possible agricultural production is at least in the neighborhood with what it would take to produce sufficient quantities of biofuel to free us from fossil fuels.

Still, it doesn’t need to be pointed out that we don’t need to nuke our soil with incessant corn production. Nor can we cease our agriculture for our other purposes. We need food. We need corn syrup for almost every industrial process imaginable relating to organic substances. The rest of the world needs our food too. We can’t be giving 90% of that up to get rid of oil.

You might protest that we’ll only need some fraction of our oil replaced by biofuels. 10-20% replacement is a good start. But the problem is, that's where it will stop too. What happened to “energy of the future?”. So we’ll be needing 80-90% of that oil after all? The goalposts have moved then. This won't be making us "energy independent" by any stretch of the imagination. And we’ll have to give up 10-25% of our farmland to achieve this? (And, assuming the economics of the situation don’t change, we’ll have to be subsidizing it at that!) Doesn’t sound like much of a deal to me. To pretend that it will replace oil feels too much like an agricultural scam.

If you want to replace oil, I mean actually replace the energy behind it, you’ll have to turn to a different source. But at least, after examining the concept, I won’t laugh as hard as I was laughing. At least it isn't windmills.

Steven Den Beste at USS Clueless blog (now, unfortunatel, inactive) has written several posts on alternative energy, mostly him raising similar objections to the ones I have raised, but with far more eloquence. http://denbeste.nu/cd_log_entries/2004/07/Justdoit.shtml. Somewhere in one of his three articles I thought I saw something on bio-diesel. Not sure though. And, though he thinks large-scale nuclear power production is an insurmountable marketing obstacle in the short term, I believe, as stated in my previous posts on energy, that the prospect of going back to the 17th century in the long term (100 years or so) is a highly persuasive marketing force.

2 Comments:

You might want to keep track of the differences in the various nomenclatures your using in your posts :o)

Bio-Diesel is a single type of biofuel, while biomass is the overall catagory :o)

I'd also note not to get 'hooked' on corn/soybeans or other 'food' plant production for the production of biofuels, that's a 'marketing' trick for corn/soybean agriculture interests. You can produce ethanol BETTER and easier from plants other than corn. Really, if we actually WANT to get serious about production of biofuels we don't want to use 'ordinary' agriculture in the first place. Your right that even intensive 'standard' agriculture is grows biomass way to slow. But that isn't the only way to grow biomass for fuel production.

There is some comment on other methods here:http://www.setamericafree.org/

and specifically here:http://ambivalentengineer.blogspot.com/2005/08/slime-farms.html

We spent a lot of money and time on research and testing on production of biomass AND biofuels from algae sources in the 80s and 90s. We can produce huge amounts of algea, (though most of our R&D was focused on the 'wrong' production methods of open pond, outdoor growing) which in turn can be (onsite) turned various forms of biofuels much more effciently and cost effectivly than using 'food' type plants.

"The oil business is so huge, and leverages such a massive prehistoric biological mechanism, that replacing our oil imports will eventually involve re-engineering our environment in the same way that we have done with building big dams, draining big swamps, and farming the prairie. We are never going to produce meaningful amounts of fuel from farm crops, because there is not enough land, not enough fresh water, and land plants produce too much non-fuel mass to sort through."

Well, he seems to have the right idea as to the degree of scale required. Thank you for the comments and the links.

If I come off as a stick-in-the-mud pessimist, it's just because I've contended with a lot of ideas before (such as this corn/soybean biodiesel stuff) that can't work. The fact that people who know it can't work push it anyway also annoys me.